# Faster than light communication

• Ian75
In summary, the conversation discusses the concept of faster than light communication using a rotating cylinder. It is mentioned that the cylinder is not perfectly rigid and it would take time for the force to be transported from one end to the other, making superluminal speed impossible. The analogy of a flashlight and a water hose is used to explain this concept. The idea of twisting the cylinder is also brought up, but it is noted that this would still not result in faster than light communication. A resource on the topic is provided and the conversation is closed due to violating forum rules.

#### Ian75

Imagine a small cylinder with a dot at the top. Rotating the cylinder 1 degree clockwise of 0 degrees could signify a 1; and 1 degree anticlockwise of 0 degrees a zero. 0 degrees would be a space.

Someone rotating one end of the cylinder would cause the other end of the cylinder to rotate instantly. Now imagine the cylinder extended to the length of one light year. Rotating one end of the cylinder would cause the other end to rotate instantly, yet a signal sent from the same end and traveling at the speed of light would take one year to arrive. This would be faster than light communication - or am I missing something really obvious?

Ian75 said:
This would be faster than light communication - or am I missing something really obvious?
Yes. This (flagged by me):
Ian75 said:
Rotating one end of the cylinder would cause the other end to rotate instantly
Instantly is wrong. It takes time to transport the force from one end to the other end and this is even slower than the speed of light. The cylinder is only kept in one piece by electromagnetic forces on molecule level. So an action on one end has to be transported via this chain to the other end.

sophiecentaur
Nothing is perfectly rigid.

sophiecentaur
This is very similar to the thought experiment of taking a flashlight and sweeping it. Far enough away, the argument goes, the light beam would sweep with superluminal speed. But, what actually happens is that the beam of light behaves more like a waterhose at that point.

sophiecentaur
Ian75 said:
Someone rotating one end of the cylinder would cause the other end of the cylinder to rotate instantly.
Think of a cylinder made of jello. If you rotate one end then you will set up a torsion wave that moves so slow that you can see it.

Steel isn't perfectly rigid, and on relativistic it would be like jello.

This thread is attracting FTL posts which are violations of PF rules, so I'm going to go ahead and close it.

## What is faster than light communication?

Faster than light communication is the concept of transmitting information or messages at a speed greater than the speed of light, which is approximately 299,792,458 meters per second. This is currently believed to be impossible according to the laws of physics.

## Is faster than light communication possible?

At this time, there is no evidence to suggest that faster than light communication is possible. The theory of relativity, proposed by Albert Einstein, states that nothing can travel faster than the speed of light. So far, all experiments and observations support this theory.

## What are some proposed methods of faster than light communication?

Some proposed methods of faster than light communication include quantum entanglement, wormholes, and tachyons. However, these are all purely theoretical and have not been proven to exist or function as a means of communication.

## Why is faster than light communication important?

Faster than light communication has been a topic of interest for scientists and science fiction writers for decades. If it were possible, it could revolutionize how we communicate and send information, making long-distance communication and space travel much more efficient. However, it is important to note that it is currently believed to be impossible.

## What are the potential consequences of faster than light communication?

If faster than light communication were possible, it could potentially violate the laws of causality, as information could be transmitted backwards in time. This could have major implications for our understanding of the universe and could potentially lead to paradoxes and other unforeseen consequences.